[oldman]

I have used them the last couple years. They put out a fair amount of light without impacting the electric bill too much.

My setup was a 600w unit for four flats (20x10) on one big heat mat and two more groups of 4 with just the 600w led light. I went with full spectrum for all of them. The lights started about 20" above the flats and were raised as the plants grew. I did move flats around too so that it wasn't the same plants directly under the fixture all the time.

I gave them about 9 hours of light a day and had good germination and almost no seedling loss. I got a timer to use with the lights, but found it easier to just turn the power strip on and off myself. Supposedly the output from the LEDs will weaken over time, but I haven't seen any noticeable change.

The startup costs are steeper, but there aren't aren't bulbs to buy and the units are sturdier (but heavier) than fluorescent lights. Rather than hang mine I put them on wire mesh shelving which worked well for me.

There are some deals to be had on ebay., especially if you're willing to buy from a Chinese vendor and wait to have it shipped. Another possibility is police auctions. They occasionally show up there as impounded property of illegal pot growers.